mpg321 is a completely Free drop-in replacement for mpg123. It has been designed to work as a drop-in replacement for mpg123, for the use of front ends, shell scripts, etc. It does all mp3 decoding using the high-quality integer-only MAD library.
The OSALP is a C++ class library that contains everything one needs to build an audio application. It contains a powerful chaining concept so programmers can build an audio application by selecting the building blocks they need.
ReZound aims to be a stable, open source, and graphical audio file editor primarily for but not limited to the GNU/Linux operating system.
Sweep is an audio editor and live playback tool. It supports PCM (WAV, AIFF etc.), Ogg Vorbis, Speex and MP3, with multichannel editing and LADSPA effects. Inside lives a pesky little virtual stylus called Scrubby who enjoys mixing around in your file
RetroCode(tm) is a universal mobile content converter. RetroCode(tm) is able to read and write most common sample based ringtone formats including meta-data. Formats: SMAF (MA2,MA3,MA5,MA7), RMF, MFM, CMX, QCP, AMR (NB,WB), AAC, MP3, OGG, SWF, RA, WAV